Eligible participants will be assigned by chance (like a coin toss) to one of three groups: (1) 1200 mg of calcium from dietary sources and 1 capsule of 400 IU vitamin D supplement everyday after the first meal of the day; (2) 450 mg of calcium from dietary sources, 2 tablets of 250 mg calcium citrate supplement and 1 capsule of 800 IU vitamin D supplement everyday after the first meal of the day and 1 tablet of 250 mg calcium citrate supplement after the evening meal or snack; or (3) unrestricted calcium from dietary sources and 1 capsule of 400 IU vitamin D supplement everyday after the first meal of the day. Participants have an equal chance of being assigned to any of these three groups until 26 participants have been assigned to group (3). At this time participants will continue to be assigned by chance to either of the two remaining groups only.